Dobby mechanism



United States Patent [72] Inventor Thomas lllndle 3,115,899 12/1963 l-lindle 139/76 Ir"; ntackbumhahl FOREIGN PATENTS g 2: 1968 980,025 1/1965 Great Britain 139/76 [45] Patented Nov. 24: 1970 Primary Examiner-James Kee Chi [73] Assignee llindle, Son 8: Company Limited, Attorney- Roberts, Cushrnan and Grover Blackburn, England [32] Priority Sept. 2, 1967 [33] Great Britain [31] 1 No. 40230167 ABSTRACT: A Leeming-type dobby or head motion having a [54] BOBBY MECHANISM plurality of axially shiftable segment gears, a crank gear cor- 7 chi-k a bum. '5 respondlng to each such segment gear, and a shifter whereby the segment gears are adjusted axially into or out of engage- [52] 0.8." v ment with their respective crank gears, also includes a dwell 1/00 plate in respect of each segment gear, the dwell plate being 77, fotalable the segment gear and being engageable a v 56 lock-tooth on the cooperating crank gear so as to prevent rotation thereof. The shifter is nonrotatable and engages [s6] 1 (med between the segment gear and the dwell plate, or between NITE STATES PATENTS such plate and a boss upon which the segment gear is 1,371,564 3/1921 Leeming 139/76 mounted.

Sheet Prior Ari Tye/was IVDL BY warm- M Patented Nov. 24, 1970' 3,542,083

Sheet '5 of5 prior 4,./ rior 41 5 V M. 6} THOMAS HI hLZZ E Patented Nov; 24, 1970 Sheet 5: 015

INVENTOR: 7"HOMAS HINDLE BY W g /M 0 Patented Nov. 24, 1970 Sheet 5 of 5 |NVENTOR:

Fig.7

77mm H/NDLE m @M W U-7J 1 BOB ME HANISM This invention relates to Lee'ming ,or-L'e'eming-type dobbies,

or head-motions, in which 'a plurality of continuously rotating segment-gears are adapted to slide along their splined driving shaft (or shafts) so asiindependently'to engageor disengage a corresponding number" of crank-gears, whichjbytheir consequent half rotations, actuate jack-levers, by which the dobby carries out its funetions,*e.g.', the heald shafts'are lifted and lowered-through the medium of streamer connections; pulleys andtie-ups; The intermittent engagement of the segme'ne gears andcrank-gears takesplaceunder the control of a pattern-chain, or. equivalent sensing device, in which the desired order of gear and jack-lever movements isrecord'ed for serial sequence.

Each segment-gear is independently. "shifted along the splined shaft by a shifter which,-while,suitably restrained from rotating with the segment-gear, is given thenecessary lateral i movement by a cam-lever having cam-grooves adapted to engage two diametrically opposite pins fixedin theshifter', which 3 pins may be fitted .with antifriction rollers towork'in the said cam-grooves.

The cam-levers swing one common fulcrum=bargand-are I adapted to befindepe'ndently lifted, either by the pattern chain t or by a relay mechanisin'controlled by the'pattern chain in the" 7 manner, described in our prior British Pat: No. 904,322," 2

thereby shifting the segment gears laterally into their engaging position,-or, conversely, to be'lowere'd, usually bygravity'with" some spring assistance, thereby shifting the segment-gears;

. back into their nonengaging position.

Each segment-gear is provided in the usual manner with gear teeth on about one-half of its periphery while the remainder has an arcuate profile adapted'to engage,vwith working clearance, theconcave outer profile of one or the other of two large lock-teeth formed, diametrically opposite to"- 3 eachother, on the crank-gear,

At all times, except when the segment-gears and their coacting crank-gears are turning with their teeth in mesh, the crankgears are locked in one or the-other of'tl'ieir dead-centre positions, so as to prevent their unwanted rotation until further changes areini'tiated by the pattern-chain;Asstated, this locking actioni's achieved-.ByJtheconcave outerjend ofeither of the, two lock-teeth on; the crank-gear"beingengaged bya' suitable arcuate profile throug ho'ut the angle ofheald-shaft dwell. it is while the crank-gears are lockedandflheld stationary in this manner that the rotatingsegrnenvgears are shiftedalong their shaft in'readiness for thenextchange of shedding and, as will be shown, the relative ease with which the se'g-y ment-gears can be soshifted laterally depends, to a major ex-,

tent, upon whether'the said arcuate profile whichprovides the" locking action is rotary or nonrotary.

Theoretically, thereis' zero torque reactio'n'on-th'e crankgear when its crankpin hascompleted its'half-gturnandit is locked'and held stationary with the crank-on dead-centre. In

practice, however,- with known} construction the' friction between the engaged'locking surfaces, especially when weav- I l ing heavy clothin wide looms, causes appreciable resistance to lateral movement: Moreovergsuch lateral frictional re sistance acting'atthe'arcuate locking radius'se'ts-up aforcecouple whichtendsto bind the comparatively narrow seg-' ment-gear unit on its splin'ed-shaft; thereby" amplifying the 1 and thepossibility of derangementof the" lateral resistance mechanism.

When a segment-gear is infull alignment with its coacting' crank-gear and has-turned-intoits angle of dwell, one of the latterslock-teeth is engaged and locked by thearcuatedwell be supported on two-ormore'through-bars 6.. The segmentgear 1 is moved laterally along shaft 7, to and fro between the nonrotating shifter, as is clearly shown in FIG. 2 theaccom panying drawings: further referredto below. In these circumstances, therefore, there is'no compensatory rotary sliding movement between the engaged locking surfaces, and consequently their full frictional resistance to movement impedes the lateral movement of the segment-gear over the whole of such movement and in both directions.

The object of this invention is to provide an improved con- V struction of combined segment-gear andshifter, whereby the frictional resistance between the engaged locking surfaces .does not appreciably impede the normal lateral to and fro .on the crank-gear, whenever this is dwelling in a dead-centre positioinis engaged andlocked by the arcuate'profile of the segment-gear and/or the equivalent circular profile of the said dwell-disc, both .ofwhich-are constantly rotatingwhen the do'bby is being operated, the arrangement beingsuch that the lock-tooth does -.not contact any'part of the nonrotating shifter.

The ii'ivention is apractical application of the well-known physical phenomenon, viz-that when a cylindrical plunger, capableo f both rotary and reciprocatory movement in a bored guide, is constantly rotated by other power means, theplunger offers little or no frictional resistance to longitudinal sliding movement. I I g I The inventionwill now be'described further, by'way of example only with' reference to the accompanying drawing illustrating-one embodiment thereof and in which: 4

FIG. 'lis a section taken through a known form of segmentgear and shifter, with the segment-gear in a position of alignrnent with thecrank-geafr;

' FIG. 2 is a similar view to FIG. 1 but with the segment-gear out of alinement with'the'cr'a nl gear; I

F1653 is a, front elevation-of the arra'ngement'shown in FIGS.14,- 5 and 6 are views corresponding respectively to FIGS..'1, 2 and 3 andshow a firstforrh segment-gear and shifter according to the invention; and

FIGS. 7 and 8-are views corresponding respectively to FIGS.

4 a'ndS of a second embodiment of the invention.

Referring now tothe drawings, and'particularly to FIGS. 1 to 3, thereof, a segmentfgear 1 is attached by screws or rivets .to a boss 2, which boss has a sliding fit on the splined driving shaft [The boss 2 is provided with a small lip 2a which retains the nonrotating shifter 3 in position thereon. The segment .gear has gear teeth 1a 'onabout one-half of its periphery, while the remainder has an'arcu'ate dwell profile, the radius of which dwell profile is approximately, equal to the pitch circle radius of the gear teeth la. e

- The segment-gear coacts in the usual manner with the crank-gear 4, which is thereby' intermittentlyfrotated on the stub-axle pin 40, fixed inspiderS, any number of whichmay position'shown in FIG! and'jthat shown in FIG.'2, by the profile of the rotating segment-gear. In these circumstances therefore, that profile is in rotary sliding-contact with the concave profile of the IOCketOOth throughout theangle of dwell,

and consequently the frictional resistance to lateral movement of thesegment-gearis negligible insofar-as the locking sur faces are concerned. v

When, however; thesegment=gear is shifted laterally out of alignment with the crank-gear, the necessary locking action is' provided, in known construction, by the arcuate profile of the shifter 3', which is suitably restrained from -rotating,'and is actuated ina'lateraldirectionby a camlever C.

Iln the position shown by FIG. 1, the rotating arcuate dwell profileof the segment'gear 1 is in engagement at L with one of the two lock-teeth 4t formed on the crank-gear 4 butjlateral movement of the segment-gear and shifter to the right (i.-e.,

' towards the position shown'in FIG. 2) at once brings the nonrotating shifter 3' into increasing contact with the lock-tooth 41, until as shown by FIG. 2, thelock-tooth is wholly engaged at L by the arcuate profile of the nonrotating shifter 3.

With the known constructionshown by FIGS. 1, 2 and 3, as above explained, the full frictional resistance to movement between the engaged locking surfaces at L impedes the lateral movement of the segment-gear from one position to the other, and is liable to cause the segment-gear to bind on the shaft.

Referring now to FIGS. 4, and 6, which show one form of the improved construction, the principal difference from the known construction shown in FIGS. 1, 2 and 3; rests in the provision of the dwell-disc 9, with the shifter 3 loosely interleaved between the said dwell-disc and the segment gear 1, which dwell-disc and segmentgear are fastened together by screws or rivets as indicated at 1b. The external radius of the dwell-disc is the same as that of the segment-gears arcuate dwell profile, while the external radius 3s of the shifter 3 is such that it does not extend to the contact line L.

At appropriate times, the concave profile of the adjacent lock-tooth 4: on the-coacting crank-gear 4 is engaged and locked by the segment-gear 1 and/or the dwell-disc 9, as these are laterally moved, in one unit, from one position to the other. During such locking engagement, the arcuate dwell profile of the segment-gear 1 and/or the equivalent circular profile of the dwell-disc 9 are in continuous sliding contact with the concave profile of the adjacent lock-tooth, therefore the frictional resistance of such engaged surfaces to additional movement in a lateral direction is negligible, and consequently the normal lateral to and fro movements of the segment-gears along their splined shaft are not appreciably impeded.

in a modification, shown byFlGS. 7 and 8, with the same practical effect, the positions of the dwell-disc and the shifter shown by FIGS. 4 and 5 are transposed.

lclaim:

1. A Leeming-type dobby or head motion comprising a plurality of axially shiftable segment gears rotatable about a predetermined axis, each segment gear having a toothed portion and an arcuate portion, a crank gear associated to each segment gear, eachcrank gear having a toothed portion engageable with the toothed portion of the segment gear and lock teeth having arcuate end faces the radii of curvature of which corresponds substantially to the radius of the arcuate portion of the segment gear engageable with said arcuate portion of the segment gear and a shifter for each segment gear adapted to effect an axial displacement of the segment gear into or out of engagement with its associated crank gear, characterized in that a dwell plate is associated with each segment gear and for rotation therewith, the said dwell plate having a peripheral face of-a constant radius adapted to be selectively engaged with a lock tooth on the associated crank gear to prevent rotation thereof.

2. A dobby or head motion as claimed in claim 1 wherein the nonrotatable shifter is located intermediate the segment gear and its related dwell plate and is so dimensioned and arranged as to preclude locking engagement thereof with the v crank gear.

3. A dobby or head motion as claimed in claim I wherein the dwell plate comprises a circular disc arranged coaxially with the segment gear.

4. A dobby or head motion as claimed in claim 1, wherein the dwell plate and segment gear define a peripheral groove therebetween to receive the nonrotatable shifter.

5. A dobby or headmotion as claimed in claim 1, wherein the shifter is disposed at that side of the dwell plate remote from the segment gear.

6. A Leeming-type dobby or head motion comprising a plurality of axially shiftable segment gears, each segment gear having an arcuate portion and a toothed portion, a crank gear associated witheach segment gear, each crank gear having a toothed portion engageable with the toothed portions of seg- I ment gear and lock teeth for engagement with the arcuate portions of the segment gear, said lock teeth having arcuate end faces the radii of curvature of which correspond substantially to the radius of the arcuate portion of the segment gear, a dwell plate associated with each segment gear and mounted for rotation therewith; said dwell plate having a peripheral face of a constant radius adapted to be selectively engaged with the faces of the lock teeth on the cooperating crank gear to prevent rotation thereof, and a shifter for each segment gear adapted, to effect an axial displacement of the segment gear into or out of engagement with its associated crank gear,

the said shifter extending directly between the dwell plate and associated segment gear and being so dimensioned and arranged as to preclude locking engagement thereof with the crank gear.

7. A Leeming-type dobby or head motion comprising a plurality of axially shiftable segment gears, each segment gear having a toothed portion and an arcuate portion, a crank gear associated with each segment gear, each crank gear having a toothed'portion adapted to-be engaged with the toothed portion of the segment gear and lock teeth having end faces the radii of curvature of which correspond to the radius of the arcuate portion of the segment gear, a dwell plate associated with eachsegment gear and mounted for rotation therewith, said dwell plate having a peripheral face of a constant radius adapted to be selectively engaged with a lock tooth on the associated crank gear to prevent rotation thereof, and a shifter for each segment gear adapted to effect an axial displacement of the segment gear into or out of engagement with its associated crank gear, the said shifter engaging a groove between a flanged boss upon which the segment gear is mounted and the dwell plate and at that side of the latter remote from the segment gear. 

